RESUMO
To analyze the shape of CMAP of both median and ulnar nerves in apparently healthy individuals, and the anatomical innervations of small muscles of hand in cadavers. Motor conduction studies of both median and ulnar nerves for 300 apparently healthy adults were performed. The nerve supply of both thenar and hypothenar muscles were dissected in 10 adult cadavers. The mean amplitude and the mean distal latency [MDL] of the median nerve were significantly higher than that of the ulnar nerve [11.785 +/- 5.0, 10.45 +/- 2.96 mV respectively, and 3.38 +/- 0.41 and 2.698 +/- 0.40 ms respectively]. The median nerve had mostly dome shaped rather than double peaked CMAP [p=0.0001], while in the ulnar nerve it was more frequently double peaked [p=0.0001]. The MDL of the median nerve was significantly longer in those with dome shaped CMAP, while in the ulnar nerve it was significantly longer in those with dome shaped [p=.0001]. There were no statistical significant differences between the amplitude of dome and double peaked CMAP in either median or ulnar nerve.. The anatomical results showed that abductor pollicis brevis is supplied by the median nerve in 90% of specimens, and by both nerves in 10%. The abductor digiti minimi brevis is supplied by the deep branch of the ulnar nerve in 90% and by superficial branch of the ulnar nerve in 10%. There was a connection between the median and ulnar nerves in 50% of specimens. Variability in the pattern of innervations of the small muscle of the hand could be a possible etiological factor for the difference in the CMAP configuration of the median and ulnar nerves